Under the Microscope

Lyme Disease and Other Tick-borne Diseases

Of the 15 species of tick that have been identified in Maine, only the deer tick, I. scapularis, is responsible for the vast majority of tick-borne illnesses affecting humans or domestic animals. These diseases, in order of frequency, are:

Lyme disease: Lyme disease is the most common of the tick-borne diseases. In 2014 the Maine CDC reported 1,395 confirmed cases. The US CDC estimates only 1/10th of true cases are reported.

Anaplasmosis: In 2014, 191 cases of anaplasmosis were reported in Maine. Anaplasmosis is a growing veterinary problem as well. Dogs develop fever, joint pains, and lack of appetite, while fever, depression, lack of appetite and occasionally ataxia are seen in horses. Anaplasmosis is increasing and continues to spread in Maine.

Babesiosis: Babesiosis has been fairly common along the southern New England coast and on Long Island for decades, and is now showing up in Maine where Lyme disease is also occurring. In 2014, 42 cases were reported in Maine.

Powassan Encephalitis: Powassan Encephalitis is usually a serious viral infection of the brain and the tissues surrounding it that leaves half its victims with permanent neurological damage and is fatal for 10%-15%. The chances of contracting this disease, however, are very low. So far, Maine has recorded five cases, including the first fatality in 2014.

Lyme Disease

In 70-80% of infected individuals, a rash expanding from the tick bite and exceeding two inches in diameter will appear within a few days up to three weeks after the tick bite. As the rash expands it may develop paler bands, giving it a "target" appearance. Occasionally, similar satellite rashes may appear on other parts of the body.

The initial symptoms of Lyme disease are fatigue, malaise, muscle aches and pains, headache, chills, fever. Untreated, additional symptoms may occur including hot swollen joints, paralysis of one side of the face (Bell's palsy), shooting pains and dizziness caused by disturbances in cardiac rhythm. Most symptoms of Lyme disease respond to antibiotic treatment.

Ten to 20% of treated Lyme disease patients may continue to have muscle and joint pains and fatigue that persist for weeks or months despite eradication of the spirochete. The cause of these symptoms is unknown, but may in part reflect an autoimmune response in which residual antibodies attack tissues.

If Lyme disease is suspected, it is important to get treated early.Antibiotic treatment is very effective and can prevent later, more serious complications.

Anaplasmosis

Like Lyme disease, anaplasmosis is transmitted via the bite of an infected deer tick, and can range from very mild to very severe illness. Symptoms include fever, headache, anorexia, nausea, muscle pain and vomiting typically within 1-2 weeks of being bitten. More severe cases may result in respiratory failure, meningitis, bleeding and kidney failure. Those who are older or who have compromised immune systems are likely to suffer a more serious illness.

While many persons infected with Anaplasma have no symptoms at all, approximately one percent of diagnosed cases will end fatally—which is why it is very important to be seen early by a physician. As with Lyme disease, early antibiotic treatment is extremely effective.

Babesiosis

Beginning within a week of exposure, symptoms can include fever, fatigue and anemia lasting several days to several months. Many of those infected may not show any sign of the disease. As it may persist in the blood for months, the disease can be transmitted by a healthy blood donor to another person.

Anyone can get babesiosis but it occurs most frequently in the elderly, in people who have had their spleen removed and in those whose immune systems are impaired. For these individuals, babesiosis can be a very serious illness with high fevers, sweating, and jaundice, followed by failure of the kidneys and other organs. The disease is treatable, so early diagnosis and treatment is imperative.

Powassan Encephalitis

Symptoms may come on suddenly within 2 days to two weeks following tick bite and include headaches, fever, nausea and vomiting, stiff neck, sleepiness, confusion, breathing distress, seizures and coma.

A similar disease is caused by two strains of the same virus: one (Powassan virus) that is transmitted by the woodchuck tick (I. cookei) and the squirrel tick (I. marxi), and a newly-recognized strain (deer tick virus) that is transmitted by the deer tick. There is no delay between the tick bite and transmission of these viruses.

Although no specific treatment for Powassan Encephalitis exists, hospitalization with supportive care may be life-saving.